U.S. patent number 8,866,044 [Application Number 13/100,497] was granted by the patent office on 2014-10-21 for system and method for manufacturing magnesium body panels with improved corrosion resistance.
This patent grant is currently assigned to GM Global Technology Operations LLC. The grantee listed for this patent is Jon T. Carter, Anil K. Sachdev. Invention is credited to Jon T. Carter, Anil K. Sachdev.
United States Patent |
8,866,044 |
Sachdev , et al. |
October 21, 2014 |
System and method for manufacturing magnesium body panels with
improved corrosion resistance
Abstract
A magnesium alloy panel for a vehicle includes a first region
and a second region extending from the first region to an edge. The
first region has a first microstructure having a first corrosion
resistance. The second region has a second microstructure different
than the first microstructure and has a second corrosion resistance
greater than the first corrosion resistance. A system for mass
producing magnesium alloy panels includes a forming apparatus and a
laser cutting apparatus. The forming apparatus forms a panel having
a first microstructure having a first corrosion resistance. The
laser cutting apparatus cuts the panel to form the edge using a
laser, and forms the second microstructure while forming the edge.
The second microstructure is different than the first
microstructure and has a second corrosion resistance greater than
the first corrosion resistance. A method for mass producing
magnesium alloy panels is also provided.
Inventors: |
Sachdev; Anil K. (Rochester
Hills, MI), Carter; Jon T. (Farmington, MI) |
Applicant: |
Name |
City |
State |
Country |
Type |
Sachdev; Anil K.
Carter; Jon T. |
Rochester Hills
Farmington |
MI
MI |
US
US |
|
|
Assignee: |
GM Global Technology Operations
LLC (Detroit, MI)
|
Family
ID: |
47019792 |
Appl.
No.: |
13/100,497 |
Filed: |
May 4, 2011 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20120280535 A1 |
Nov 8, 2012 |
|
Current U.S.
Class: |
219/121.72 |
Current CPC
Class: |
B23K
26/38 (20130101); B23K 2101/006 (20180801); B23K
2103/15 (20180801) |
Current International
Class: |
B23K
26/40 (20140101) |
Field of
Search: |
;148/525,565,666,667
;219/121.72,121.67,121.65,121.66,121.8 ;72/47 |
References Cited
[Referenced By]
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Foreign Patent Documents
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Other References
Machine translation of Japan Patent Document No. 2010-023,051-A,
Sep. 2013. cited by examiner .
Machine translation of Japan Patent document No. 2002-363,721, Feb.
2014. cited by examiner .
Machine translation of Japan Patent document No. 2006-88,435, Feb.
2014. cited by examiner .
Ignat et al. , "Magnesium alloys laser (Nd:YAG) cladding and
alloying with side injection of aluminum powder", Jan. 2004,
Elsevier, Applied Surface Science, vol. 225, pp. 124-134. cited by
examiner .
Gray et al., Protective coatings on magnesium and its alloys--a
critical review , Jan. 2002, Elsevier, Journal of Alloys and
Compounds vol. 336, pp. 88-113. cited by examiner.
|
Primary Examiner: Evans; Geoffrey S
Attorney, Agent or Firm: Harness, Dickey & Pierce,
P.L.C.
Claims
What is claimed is:
1. A manufacturing system for mass producing magnesium alloy
panels, comprising: a forming apparatus configured to form a panel
comprising magnesium having a three dimensional shape and a first
corrosion resistance; and a laser cutting apparatus comprising a
laser and a feeding apparatus, wherein the laser is configured to
cut the panel to form an edge comprising a molten material, and the
feeding apparatus is configured to introduce an alloying element as
a solid wire to the molten material adjacent to a region of the
panel where the laser cuts so as to create an intermetallic phase
in the region to provide a second corrosion resistance greater than
the first corrosion resistance.
2. The manufacturing system of claim 1, wherein the panel
comprising magnesium has N phases and the region of the panel
having the second corrosion resistance has N+M phases, N and M
being integers greater than zero.
3. The manufacturing system of claim 1, wherein the panel
comprising magnesium further comprises aluminum, zinc, tin,
manganese, or combinations thereof.
4. The manufacturing system of claim 1, wherein the alloying
element is an alloying element present in the panel as received by
the laser cutting apparatus.
5. The manufacturing system of claim 1, wherein the alloying
element is not present in the panel as received by the laser
cutting apparatus.
6. The manufacturing system of claim 1, wherein the forming
apparatus forms the panel using one of a stamping process and a hot
metal gas forming process.
7. The manufacturing system of claim 1, wherein the forming
apparatus forms the panel by casting the panel.
8. The manufacturing system of claim 1, wherein the alloying
element is selected from a group consisting of: aluminum, zinc,
tin, manganese, rare earth metals, magnesium, and combinations
thereof.
9. The manufacturing system of claim 1, wherein the panel comprises
an alloy of magnesium, aluminum, and zinc.
10. The manufacturing system of claim 9, wherein the intermetallic
phase comprises Mg.sub.17Al.sub.12.
11. A method for mass producing magnesium alloy panels, comprising:
forming a panel comprising magnesium having a first corrosion
resistance; cutting the panel to form an edge comprising a molten
material using a laser; and introducing an alloying element as a
solid wire to the molten material adjacent to a region of the panel
where the laser cuts so as to create an intermetallic phase in the
region to provide a second corrosion resistance greater than the
first corrosion resistance.
12. The method of claim 11, further comprising forming the panel
using one of a hot metal gas forming process, a stamping process,
and a casting process.
13. The method of claim 11, wherein the panel comprising magnesium
further comprises aluminum, zinc, tin, manganese, or combinations
thereof.
14. The method of claim 11, wherein the introducing of the alloying
element is to the molten material in a cutting area generated while
cutting the panel to form the edge using the laser.
15. The method of claim 14, wherein the alloying element is not
present in the panel when forming the panel.
16. The method of claim 14, wherein the alloying element is an
alloying element present in the panel when forming the panel.
17. A manufacturing system for mass producing magnesium alloy
panels, comprising: a forming apparatus configured to form a panel
comprising magnesium having a three dimensional shape and a first
corrosion resistance; a laser cutting apparatus comprising a laser
and a feeding apparatus, wherein the laser is configured to cut the
panel to form an edge comprising a molten material, and the feeding
apparatus is configured to introduce an alloying element as a solid
wire to the molten material adjacent to a region of the panel where
the laser cuts so as to create an intermetallic phase in the region
to provide a second corrosion resistance greater than the first
corrosion resistance; and a finishing apparatus configured to apply
a surface treatment to the panel, wherein the finishing apparatus
is further configured to selectively omit applying the surface
treatment to the edge.
18. The manufacturing system of claim 17, wherein the panel
comprising magnesium has N phases and the region of the panel
having the second corrosion resistance has N+M phases, N and M
being integers greater than zero.
19. The manufacturing system of claim 17, wherein the panel
comprises an alloy of magnesium, aluminum, and zinc.
20. The manufacturing system of claim 19, wherein the intermetallic
phase comprises Mg.sub.17Al.sub.12.
Description
FIELD
The present disclosure relates to systems and methods for
manufacturing metal panels for vehicle bodies, and more
particularly, to manufacturing systems and methods for producing a
finished edge on magnesium body panels having improved corrosion
resistance.
BACKGROUND
The background description provided herein is for the purpose of
generally presenting the context of the disclosure. Work of the
presently named inventors, to the extent it is described in this
background section, as well as aspects of the description that may
not otherwise qualify as prior art at the time of filing, are
neither expressly nor impliedly admitted as prior art against the
present disclosure.
Many automotive body panels are mass produced from wrought sheet
metal, typically wrought steel alloys using a stamping process
carried out by a stamping press. During the stamping process, a
work piece is formed to a desired shape and cut to produce a sheet
metal part. More specifically, forming dies are brought into
contact with the work piece to deform the work piece into the
desired shape and cutting dies shear the work piece.
Some automotive body panels are mass produced from cast metal using
a casting process carried out by a casting machine. Typically, the
metal is an alloy of aluminum or magnesium, and the casting process
is a high-pressure die casting process. During the casting process,
molten metal is poured into a mold defining a semi-finished shape
of the panel and allowed to cool to solidify. The solidified part
is then removed from the mold and trimmed and/or pierced using one
or more presses and hardened tools. In automotive bodies, cast
panels conventionally are used as inner panels, rather than
exterior panels, on door assemblies and lift gates.
However, some steel alloys and cast magnesium alloys used to make
the automotive body panels have low corrosion resistance and
corrode when exposed to moisture and various substances found in
the environment, such as salt used to melt snow and ice on the
roads. Accordingly, sheet metal parts used to create the panels may
be coated with a thin layer of zinc by the steel supplier using a
galvanizing process. After undergoing the forming process, the
panels are typically cleaned and coated with a surface treatment
including, for example, phosphate, electro-deposited epoxy, and
paint. The surface treatment provides a barrier of
corrosion-resistant material between the damaging environment and
the sheet metal part.
SUMMARY
In one form, the present disclosure provides a manufacturing system
for mass producing magnesium alloy panels. The manufacturing system
includes a forming apparatus and a laser cutting apparatus. The
forming apparatus forms a panel having a three dimensional shape
and a first microstructure having a first corrosion resistance. The
laser cutting apparatus cuts the panel to form an edge using a
laser. The laser cutting apparatus forms a second microstructure in
the panel while forming the edge. The second microstructure is
different than the first microstructure and has a second corrosion
resistance greater than the first corrosion resistance.
In various features, the manufacturing system further includes a
feeding apparatus that adds an alloying element to a molten
material in a cutting area generated by the laser cutting apparatus
while cutting the panel. In one related feature, the alloying
element is an alloying element present in the panel as received by
the laser cutting apparatus. In another related feature, the
alloying element is not present in the panel as received by the
laser cutting apparatus.
In further features, the forming apparatus forms the panel by one
of a hot metal gas forming process and a stamping process. In an
alternate feature, the forming apparatus forms the panel by casting
the panel. In still further features, the panel is composed of an
alloy including at least one alloying element selected from a group
consisting of aluminum, zinc, tin, and manganese.
In another form, the present disclosure provides a magnesium alloy
panel for a vehicle. The panel includes a first region and a second
region extending from the first region to an edge. The first region
has a first microstructure having a first corrosion resistance. The
second region has a second microstructure different than the first
microstructure. The second microstructure has a second corrosion
resistance greater than the first corrosion resistance.
In various features, the first microstructure has N phases and the
second microstructure has N+M phases, N and M being integers
greater than zero. In further features, the second region includes
an intermetallic phase and a weight percentage of the intermetallic
phase is greater in the second region than in the first region. In
still further features, the second microstructure includes an
intermetallic phase including aluminum. In yet further features,
the first region is composed of a ternary alloy including aluminum
and zinc as alloying elements.
In another form, the present disclosure provides a method for mass
producing magnesium alloy panels. The method includes forming a
panel having a first microstructure having a first corrosion
resistance. The method further includes cutting the panel to form
an edge using a laser. The method further includes forming a second
microstructure in the panel while cutting the panel to form the
edge. The second microstructure is different than the first
microstructure and has a second corrosion resistance greater than
the first corrosion resistance.
In various features, the method further includes adding an alloying
element to a molten material in a cutting area generated while
cutting the panel to form the edge. In one related feature, the
alloying element is an alloying element present in the panel when
forming the panel. In another related feature, the alloying element
is not present in the panel when forming the panel. In further
features, the method further includes forming the panel using one
of a hot metal gas forming process, a stamping process, and a
casting process. In still further features, the panel is composed
of an alloy including at least one alloying element selected from a
group consisting of aluminum, zinc, tin, and manganese.
Further areas of applicability of the present disclosure will
become apparent from the detailed description provided hereinafter.
It should be understood that the detailed description and specific
examples are intended for purposes of illustration only and are not
intended to limit the scope of the disclosure.
BRIEF DESCRIPTION OF THE DRAWINGS
The present disclosure will become more fully understood from the
detailed description and the accompanying drawings, wherein:
FIG. 1 is a block diagram illustrating an exemplary manufacturing
system for mass producing sheet metal panels using a wrought
magnesium alloy according to the present disclosure;
FIG. 2 is a magnified fragmentary view illustrating an exemplary
microstructure of a wrought magnesium alloy panel according to the
present disclosure; and
FIG. 3 is a flow diagram illustrating an exemplary method for mass
producing sheet metal panels using a wrought magnesium alloy
according to the present disclosure.
DETAILED DESCRIPTION
The following description is merely illustrative in nature and is
in no way intended to limit the disclosure, its application, or
uses. For purposes of clarity, the same reference numbers will be
used in the drawings to identify similar elements. As used herein,
the phrase at least one of A, B, and C should be construed to mean
a logical (A or B or C), using a non-exclusive logical or. It
should be understood that steps within a method may be executed in
different order without altering the principles of the present
disclosure.
As used herein, the term module may refer to, be part of, or
include an Application Specific Integrated Circuit (ASIC); an
electronic circuit; a combinational logic circuit; a field
programmable gate array (FPGA); a processor (shared, dedicated, or
group) that executes code; other suitable components that provide
the described functionality; or a combination of some or all of the
above, such as in a system-on-chip. The term module may include
memory (shared, dedicated, or group) that stores code executed by
the processor.
The term code, as used above, may include software, firmware,
and/or microcode, and may refer to programs, routines, functions,
classes, and/or objects. The term shared, as used above, means that
some or all code from multiple modules may be executed using a
single (shared) processor. In addition, some or all code from
multiple modules may be stored by a single (shared) memory. The
term group, as used above, means that some or all code from a
single module may be executed using a group of processors or a
group of execution engines. For example, multiple cores and/or
multiple threads of a processor may be considered to be execution
engines. In various implementations, execution engines may be
grouped across a processor, across multiple processors, and across
processors in multiple locations, such as multiple servers in a
parallel processing arrangement. In addition, some or all code from
a single module may be stored using a group of memories.
The apparatuses and methods described herein may be implemented by
one or more computer programs executed by one or more processors.
The computer programs include processor-executable instructions
that are stored on a non-transitory tangible computer readable
medium. The computer programs may also include stored data.
Non-limiting examples of the non-transitory tangible computer
readable medium are nonvolatile memory, magnetic storage, and
optical storage.
As an alternative to steel, magnesium alloys may be used to produce
automotive body panels of high strength and reduced weight. For
example, magnesium alloys including aluminum and zinc may be used.
Although some alloying elements, such as aluminum and zinc alone
may be more corrosion resistant than magnesium, in wrought form,
magnesium alloys generally have low corrosion resistance and must
be coated with a surface treatment to inhibit corrosion. The low
corrosion resistance is due to a single phase microstructure of the
sheet metal in which the alloying elements are uniformly dissolved
in the magnesium.
Cast magnesium alloys generally contain at least two discrete
phases due to increased weight percentages of alloying elements and
phase separation during solidification. Intermetallic phases, such
as phases containing aluminum, can impart corrosion resistance to a
cast panel and, as a result, cast panels can have more corrosion
resistance than wrought panels with a similar composition. The
difference in corrosion resistance is because hot working used to
produce the wrought sheet metal dissolves the intermetallic phases
in the surrounding magnesium matrix. However, increased weight
percentages of the alloying elements can reduce the castability of
magnesium alloys. As a result, cast magnesium panels formed from
suitable alloys may not provide a desired corrosion resistance, and
may be coated with a surface treatment to inhibit corrosion.
Surface treatments can be used to provide additional corrosion
resistance to both wrought magnesium panels and cast magnesium
panels. However, the surface treatments applied to the panels are
susceptible to damage, such as chips and scratches, both during the
manufacture of the panels and while the panels are in service. The
surface treatments are particularly susceptible to damage at edges
of the panels, where the surface treatments may be thin and less
adherent and where manufacturing stresses are higher and are more
likely to damage the surface treatments.
The present disclosure provides a manufacturing system and method
for mass producing automotive vehicle panels from both wrought and
cast magnesium alloys that offer improved corrosion resistance when
compared to conventional systems and methods. The system includes a
laser cutting apparatus that alters the microstructure of the
panels while cutting the panels to form an edge. The laser cutting
apparatus heats the panel and melts a thin layer within a cutting
area that re-solidifies to create a multi-phase microstructure at
the edge. The multi-phase microstructure is similar to a cast
microstructure of the magnesium alloy and includes at least one
intermetallic phase having increased corrosion resistance. The
intermetallic phase provides the panel with improved corrosion
resistance at the edge and reduces the need to rely on surface
treatments for achieving the desired corrosion protection. The
laser cutting apparatus can replace conventional devices used to
produce a finished edge on a mass produced panel, such as shearing
dies. Although laser cutting devices are generally considered to
require more time to produce an edge than other conventional
devices, the anti-corrosion benefits disclosed herein may outweigh
any reductions to manufacturing efficiency in various
applications.
With particular reference to FIG. 1, a block diagram illustrates an
exemplary manufacturing system 100 for mass producing a sheet metal
panel 102 with improved corrosion resistance from a wrought
magnesium alloy. The manufacturing system 100 may be used to
produce panels from sheet metal having a thickness from, for
example, less than one millimeter (1 mm) to approximately thirteen
millimeters (13 mm), including all sub-ranges. As used herein, mass
production refers to production of large amounts of standardized
products for consumption by a consumer or end user, for example.
Typically, mass production will be carried out in a manufacturing
facility dedicated for such purposes, and designed to produce the
products in large quantities sufficient to meet market demand. In
the automotive setting, manufacturing facilities may be designed to
produce more than one hundred thousand units or, more particularly,
between two to three hundred thousand units.
According to the present non-limiting example, the panel 102 is
produced from a ternary aluminum-magnesium-zinc alloy, such as
AZ31, AZ61, or AZ91. Although the wrought magnesium alloy of the
present example includes alloying elements of aluminum and zinc, it
will be appreciated that in various aspects of the present
disclosure, other alloying elements are optionally used. For
example, the other alloying elements include, but are not limited
to, tin, manganese and rare earth metals. Still further, alloying
elements include those known in the art as grain modifiers and
those known in the art to modulate hardness, ductility, density,
elongation, yield strength, and the like as non-limiting
examples.
The panel 102 forms all or part of various structural and
non-structural vehicle body panels including, but not limited to,
underbody panels (e.g., floor panels and dash panels), body side
panels (e.g., quarter panels), roof panels, and body closure panels
(e.g., door, roof, and deck lid panels). Additionally, in various
aspects, the panel 102 forms all or part of an outer body panel
and/or an inner body panel. The panel 102 includes a central region
104 having a single phase microstructure and an adjoining
peripheral region 106 having a multi-phase microstructure. The
peripheral region 106 extends from the central region 104 to an
edge 108. The peripheral region 106 may extend around the panel 102
in a continuous manner as shown, or extend along selected portions
in an intermittent manner. The peripheral region 106 and the edge
108 are created using a laser welding apparatus, as discussed in
more detail below. The edge 108 may be an outer edge as shown, or
an inner edge defining an aperture or other opening within the
panel 102.
With particular reference to FIG. 2, a magnified fragmentary view
of an exemplary panel illustrates various features of the different
microstructures of the central region 104 and the peripheral region
106. For reference, a line 110 illustrates a dimension of
approximately forty micrometers (40 .mu.m). A boundary between the
central region 104 and the peripheral region 106 can be seen in
FIG. 2 and is designated by reference numeral 112. The single phase
microstructure of the central region 104 is typical of a
microstructure of a rolled sheet metal formed of a wrought
aluminum-magnesium-zinc alloy. The single phase microstructure of
the central region 104 is a physically homogeneous region in which
the aluminum and zinc alloying elements are well dissolved in the
magnesium. The single phase microstructure is distinct from the
adjoining multi-phase microstructure of the peripheral region
106.
The peripheral region 106 may be referred to as a recast layer, as
it is created during melting and re-solidification of the base
material during a laser cutting process. The peripheral region 106
includes an outer layer 114 and an intermediate layer 116. A
boundary between the outer layer 114 and the intermediate layer 116
can be seen in FIG. 2 and is designated by reference numeral 118.
The outer layer 114 includes fissures or cracks 120 that may form
as the recast layer re-solidifies. In various implementations, the
outer layer 114 is removed using an edge finishing process to give
the edge 108 a relatively smooth finish. The intermediate layer 116
is relatively free from cracks. The intermediate layer 116, alone
or in combination with the outer layer 114, has a width 122 between
one percent (1%) and one hundred percent (100%) of the thickness of
the sheet metal used to produce the panel 102, including all
sub-ranges.
According to the present non-limiting example, the microstructure
of the peripheral region 106 includes a magnesium-rich matrix phase
and an intermetallic phase including aluminum. The magnesium-rich
matrix phase includes physically homogeneous and distinct portions
in which the magnesium is the primary constituent and a weight
percentage of the magnesium is greater than that in the central
region 104. The intermetallic phase includes physically homogeneous
and distinct portions in which a weight percentage of the aluminum
is greater than that in the central region 104 and that in the
surrounding magnesium-rich matrix phase. The intermetallic phase
includes Mg17Al12 particles or lamella or other lenticular shapes
that are corrosion resistant and provide the peripheral region 106
with the increased corrosion resistance.
The intermetallic phase is present as discrete portions or islands
surrounded by the magnesium-rich matrix phase and/or is present as
a contiguous network. In various aspects, the intermetallic phase
is dispersed relatively uniformly within the magnesium-rich matrix
phase. In other aspects, the intermetallic phase increases in
distribution (i.e., frequency of occurrence) in a direction from
the central region 104 to the edge 108. In other words, a space
between the discrete portions of the intermetallic phase decreases
in a direction from the central region 104 to the edge 108. In
still other aspects, portions of the intermetallic phase are
disposed at the edge 108 and separate portions of the
magnesium-rich matrix phase from the edge 108. In various
implementations, the peripheral region 106 includes additional
intermetallic phases depending on the number of alloying elements
and various parameters of the laser cutting process.
Referring again to FIG. 1, the manufacturing system 100 includes a
work piece forming apparatus 130, a shape forming apparatus 132,
and a laser cutting apparatus 134 that cooperate to produce the
panel 102. The manufacturing system 100 further includes a surface
treatment apparatus 136, an assembling apparatus 138, and a final
finishing apparatus 140. The surface treatment apparatus 136, the
assembling apparatus 138, and the final finishing apparatus 140
cooperate to apply a surface treatment to the panel 102 and
assemble the panel 102 to another panel 142 to create a finished
panel assembly 144. In various aspects, the panel 142 is a sheet
metal panel manufactured according to the present disclosure.
Together, the panels 102, 142 form all or part of an inner and
outer panel assembly, such as door inner and outer panel
assembly.
The work piece forming apparatus 130 receives a raw material 150 to
be used to produce the panel 102 and produces a generally flat work
piece 152 that is delivered to the shape forming apparatus 132. The
raw material 150 is a wrought aluminum-magnesium-zinc alloy
material and is provided as a rolled sheet or in any other suitable
form. Generally, the raw material 150 has a single phase
microstructure and grain structure suitable for forming an overall
desired shape of the panel 102. In various implementations, the
work piece forming apparatus 130 cuts the work piece 152 from the
raw material 150.
The shape forming apparatus 132 receives the work piece 152 and
deforms the work piece 152 to produce a three-dimensional, shaped
panel 154 having an overall desired shape of the panel 102. In
various aspects, the shape forming apparatus 132 forms the shaped
panel 154 by sheet metal forming methods suitable for wrought
aluminum-magnesium-zinc alloys. For example, hot metal gas forming,
stamping, bending, curling, decambering, deep drawing, incremental
sheet forming, press brake forming, and punching methods are
suitable for use with the present teachings.
The laser cutting apparatus 134 receives the shaped panel 154 and
cuts the shaped panel 154 using one or more laser beams to produce
the peripheral region 106 and the edge 108 of the panel 102. The
laser cutting apparatus 134 is a separate apparatus from the shape
forming apparatus 132 in select aspects. Alternately, in various
aspects, the laser cutting apparatus 134 may be combined with the
shape forming apparatus 132 to improve manufacturing efficiency.
According to the present non-limiting example, the laser cutting
apparatus 134 includes an automated, industrial laser 160
controlled by a control module 162 that, together, may form a
robotic laser cutting cell. The laser 160 employs various lasers
including, but not limited to, carbon dioxide (CO2) lasers,
neodymium (Nd) lasers, and neodymium yttrium-aluminum-garnet
(Nd-YAG) lasers. The laser 160 cuts the shaped panel 154 by
directing a laser beam (or multiple beams) along a predetermined
path. In various implementations, multiple laser beams directed
along separate portions of the predetermined path are employed to
increase manufacturing efficiency. The laser 160 directs the laser
beam at predetermined linear cutting speeds to heat material
impacted by the laser 160 to a predetermined temperature above a
melting point of the material. The laser 160 causes material in the
cutting area to melt and fall away, creating a kerf that produces
the edge 108.
Generally, the laser cutting apparatus 134 performs the cutting
operation in the ambient environment of a manufacturing facility at
temperatures of around, for example, twenty degrees Celsius
(20.degree. C.). In various implementations, an inert gas is
directed towards the cutting area under pressure to blow the molten
material from the cutting area. Additionally, a feeding apparatus
164, or other suitable device, supplies an alloying element to the
molten material of the cutting area to increase a concentration of
an alloying element already present from the raw material 150
(e.g., aluminum) or add a new alloying element. In this way, the
feeding apparatus 164 is used to increase the presence and
continuity of the intermetallic phase or to create additional
intermetallic phases within the peripheral region 106 of increased
corrosion resistance. The feeding apparatus 164 supplies the
alloying element by feeding the alloying element into the molten
material of the cutting area. In various aspects, the feeding
apparatus 164 is configured to feed the alloying element as a
powder. In other aspects, the feeding apparatus 164 is configured
to feed the alloying element as a solid wire.
The control module 162 controls operation of the laser 160. More
specifically, the control module 162 controls the path and linear
cutting speeds of the laser 160. The control module 162 further
controls an energy of the laser 160. By controlling the path, the
linear cutting speeds, and the energy of the laser, a heating rate
and a melting rate within the cutting area may also be controlled.
The heating rate and the melting rate are controlled to achieve the
desired multi-phase microstructure and width (i.e., the width 122)
of the peripheral region 106. The various operating parameters,
including the linear cutting speeds and the laser energy, can be
predetermined. For example, the operating parameters can be
predetermined during a development phase of panel design and/or a
validation phase of panel manufacture, based on testing to ensure
the desired metallurgical properties of the peripheral region 106
are achieved.
The surface treatment apparatus 136 receives the panel 102 and
applies a surface treatment to the panel 102 to produce a treated
panel 170. The surface treatment provides a protective coating and
promotes adhesion of a finish layer applied by the final finishing
apparatus 140. According to the present non-limiting example, the
surface treatment is applied to the entire surface of the panel
102, including the edge 108. In alternate implementations, the
surface treatment may be selectively omitted in selected areas of
the peripheral region 106, including the edge 108.
The surface treatment includes an electro-deposition coating
applied by any electro-deposition process suitable for coating an
aluminum-magnesium-zinc alloy. For example, a suitable
electro-deposition process includes cleaning the panel 102 using a
water-based solvent, such as an acid solvent or a base solvent, and
then drying the panel 102. The panel 102 is then submerged in a
bath of an electro-deposition solution under conditions in which an
electrical potential is established between the panel 102 and paint
particles suspended in the electro-deposition solution. The paint
particles are attracted to the panel 102 and form a coating over a
portion of or the entire surface of the panel 102. The panel 102 is
then removed from the bath and heated to cure the coating.
The assembling apparatus 138 receives the treated panel 170 and
assembles the panel 142 to the treated panel 170 to produce a panel
assembly 180. In various aspects, the treated panel 170 and the
panel 142 are joined using a hemming process in which a hem is
formed to overlap the peripheral region 106. Alternately, or
additionally, the treated panel 170 and the panel 142 are joined by
a structural adhesive.
The final finishing apparatus 140 receives the panel assembly 180
and applies a finish coating to the panel assembly 180 to produce
the finished panel assembly 144. The finish coating is any coating
that provides selected areas of the finished panel assembly 144
with a desired appearance or functionality. As a non-limiting
example, the finish coating is a polymer paint coating optionally
including a base coat and/or a clear coat.
With particular reference to FIG. 3, a flow diagram illustrates an
exemplary method 200 for mass producing a sheet metal panel with
improved corrosion resistance from a wrought magnesium alloy. In
various aspects, the method 200 is implemented by a manufacturing
system, such as the manufacturing system 100 discussed above, to
mass produce a panel, such as the panel 102. Accordingly, for
simplicity, the method 200 will be described with reference to the
various components of the manufacturing system 100 and the panel
102.
A start of the method is designated at 202. At 204, the work piece
forming apparatus 130 forms the work piece 152 from the wrought
magnesium alloy of the raw material 150. At 206, the shape forming
apparatus 132 deforms the work piece 152 to form the shaped panel
154 having the overall desired three dimensional shape of the panel
102. At 208, the laser cutting apparatus 134 cuts the shaped panel
154 using the predetermined laser cutting process to form the edge
108 on the panel 102. During the laser cutting process, the laser
cutting apparatus 134 alters the single phase microstructure of the
shaped panel 154 in the peripheral region 106 to produce the
multi-phase microstructure adjoining the edge 108. In various
implementations, the method 200 may further include the laser
cutting apparatus 134 adding one or more additional alloying
elements to the molten material of the cutting area to promote the
formation and continuity of intermetallic phases. At 210, the
surface treatment apparatus 136 applies the electro-deposition
coating to the panel 102 to produce the treated panel 170. At 212,
the assembling apparatus 138 joins the panel 142 to the treated
panel 170 to form the panel assembly 180. At 214, the final
finishing apparatus 140 applies the finish coating to the panel
assembly 180 to produce the finished panel assembly 144. At 216,
the method returns to the start at 202 to begin production of
another panel 102.
According to the present disclosure, a cast panel including an edge
with improved corrosion can be formed by laser cutting an as-cast
panel or work piece. The cast panel may form all or part of various
structural and non-structural panels including, but not limited to,
vehicle body panels. The as-cast panel is formed using a casting
process suitable for casting a magnesium alloy. The as-cast panel
is cast to have an overall desired shape of the cast panel and
includes a first multi-phase microstructure formed during the
casting process. During the laser cutting process used to form the
edge, a thin layer within a cutting area melts and re-solidifies
and a second, multi-phase microstructure is created. The second
multi-phase microstructure is different from the first
microstructure and has improved corrosion-resistance. In various
aspects, the edge is an outer peripheral edge or an inner edge
defining an aperture or other opening within the cast panel.
According to the present non-limiting example, the cast panel is
formed from a ternary aluminum-magnesium-zinc alloy such as AZ63,
AZ81, or AZ91. Alloying elements of aluminum and zinc have
anti-corrosive properties and are used to facilitate the formation
of the second multi-phase microstructure. In various aspects of the
present disclosure, other alloying elements are optionally or
additionally used. For example, other alloying elements include,
but are not limited to, tin, manganese, and rare earth metals. In
one example, an aluminum-magnesium-manganese alloy such as AM60 is
used. Still further, alloying elements include grain modifiers and
other alloying elements known in the art to modulate hardness,
ductility, density, elongation, yield strength, and the like.
Weight percentages of the alloying elements are selected to provide
the cast panel with desired properties including, for example,
castability properties and mechanical properties. By forming the
edge to have a greater corrosion resistance than the rest of the
cast panel, it will be appreciated that a lower weight percentage
of one or more of the alloying elements may be used to improve
castability of the as-cast panel.
The cast panel includes a central region having the first
multi-phase microstructure and a peripheral region having the
second multi-phase microstructure. The peripheral region extends
from the central region to the edge. The central region may be
referred to as an as-cast layer, as it is created during the
casting process used to form the as-cast panel. The first
multi-phase microstructure of the central region includes at least
one intermetallic phase dispersed within a magnesium-rich matrix
phase. One or more intermetallic phases may be present depending on
a number of alloying elements of a casting material and various
parameters of the casting process. According to the present
non-limiting example, the first multi-phase microstructure includes
an intermetallic phase of Mg17Al12 particles or lamella or other
lenticular shapes dispersed throughout the magnesium-rich matrix
phase. The Mg17Al12 particles have a distribution (i.e., a
frequency of occurrence) that is based on the casting process. The
distribution can be increased or decreased by varying one or more
parameters of the casting process. For example, a casting
temperature and a cooling rate can be varied to achieve a desired
distribution.
The peripheral region may be referred to as a re-cast layer, as it
is created during melting and re-solidification of the base
material during the laser cutting process used to create the edge.
The peripheral region has a width between one percent (1%) and one
hundred percent (100%) of a thickness of the cast panel in the
peripheral region. The second multi-phase microstructure of the
peripheral region includes at least one corrosion-resistant
intermetallic phase dispersed within a magnesium-rich matrix phase.
The intermetallic phase of the second multi-phase microstructure
may be present in the first multi-phase microstructure or,
alternatively, may be an additional phase created during the laser
cutting process. Accordingly, in various aspects, the second
multi-phase microstructure includes a greater number of
intermetallic phases than the first multi-phase microstructure.
Additional intermetallic phases can be created, for example, by
adding additional alloying elements during the laser cutting
process that are not present in the as-cast panel.
According to the present non-limiting example, the second
multi-phase microstructure includes an intermetallic phase of
Mg17Al12 particles dispersed throughout a magnesium-rich matrix
phase. The Mg17Al12 particles of the second multi-phase
microstructure are present at a second distribution greater than
the first distribution of Mg17Al12 particles in the first
multi-phase microstructure. The greater distribution of Mg17Al12
particles provides the peripheral region with a greater corrosion
resistance than that of the central region. The distribution of
Mg17Al12 particles is increased by adding aluminum alloying
material to the molten material of the cutting area during the
laser cutting process. In various aspects, the distribution of
Mg17Al12 particles is increased depending on various parameters of
the laser cutting process.
According to the present disclosure, the cast panel can be mass
produced from an as-cast panel formed using a conventional casting
process for casting magnesium alloy panels. An exemplary
manufacturing system includes a suitable casting apparatus, a laser
cutting apparatus and, optionally, an edge finishing apparatus. The
laser cutting apparatus is similar to the laser cutting apparatus
134. In various implementations, the edge finishing apparatus is
used to smooth the edge created by the laser cutting apparatus. In
various aspects, the manufacturing system further includes a
surface treatment apparatus, an assembling apparatus, and a final
finishing apparatus similar to the surface treatment apparatus 136,
the assembling apparatus 138, and the final finishing apparatus
140.
In an exemplary method, the casting apparatus forms an as-cast
panel having an overall desired three dimensional shape of a
finished panel. The as-cast panel includes a first multi-phase
microstructure including an intermetallic phase dispersed in a
magnesium-rich matrix phase. In various aspects, the intermetallic
phase does not provide sufficient corrosion resistance. The laser
cutting apparatus cuts the as-cast panel using a predetermined
laser cutting process to produce a cut panel including a
corrosion-resistant edge. The laser cutting process alters the
first multi-phase microstructure of the as-cast panel, creating a
second multi-phase microstructure different from the first
multi-phase microstructure. The second multi-phase microstructure
includes a corrosion resistant intermetallic phase dispersed in a
magnesium-rich matrix phase.
In various implementations, the intermetallic phase is created by
adding an alloying element to the molten material of the cutting
area during the laser cutting process. In various aspects, the
alloying element is present in the as-cast panel or, alternatively,
is an additional alloying element having corrosion-resistant
properties. In further aspects, an intermetallic phase is present
in both the first and second multi-phase microstructures, yet has a
greater distribution within the second multi-phase microstructure.
In still further aspects, the distribution of the intermetallic
phase within a region of the second multi-phase microstructure is
relatively uniform or, optionally, increases in a direction from a
central region of the cast panel towards the edge.
The broad teachings of the disclosure can be implemented in a
variety of forms. Therefore, while this disclosure includes
particular examples, the true scope of the disclosure should not be
so limited since other modifications will become apparent to the
skilled practitioner upon a study of the drawings, the
specification, and the following claims.
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